Antigenic unheated culture filtrates of Mycobacterium kansasii, M. avium, M. gordonae, M. scrofulaceum, and M. intracellulare are being prepared and reference polyvalent goat antisera to each are being raised. Using these materials, species specific antigens will be identified, which will then be purified by immunoabsorbent affinity chromatography, supplemented by physicochemical fractionations if necessary. During the first year of work an apparently species specific, highly anodal, protein antigen of M. kansasii has been identified and isolated.